(N/A) Preparation: Calcium carbonate occurs in nature in several forms like limestone,chalk,and marble. It can be prepared by passing carbon dioxide through slaked lime or by the addition of sodium carbonate to calcium chloride.
$Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$
$CaCl_2 + Na_2CO_3 \rightarrow CaCO_3 + 2NaCl$
Excess of $CO_2$ leads to the formation of water-soluble calcium hydrogen carbonate.
Properties: It is a white fluffy powder and is almost insoluble in water. When heated to $1200 \ K$,it decomposes to evolve $CO_2$.
$CaCO_3 \xrightarrow{1200 \ K} CaO + CO_2$
It reacts with dilute acids to liberate carbon dioxide.
$CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2$
$CaCO_3 + H_2SO_4 \rightarrow CaSO_4 + H_2O + CO_2$
Uses: $(i)$ It is used as a building material in the form of marble and in the manufacture of quick lime. (ii) $A$ mixture of $CaCO_3$ and $MgCO_3$ is used as a flux in the extraction of metals such as iron. (iii) Specially precipitated $CaCO_3$ is extensively used in the manufacture of high-quality paper. (iv) It is also used as an antacid,mild abrasive in tooth-paste,a constituent of chewing gum,and a filler in cosmetics.